Vertical Twist Scheme for High Density DRAMs

ABSTRACT

An interconnection array subunit and method for forming the interconnection array subunit are provided, the interconnection array subunit including a first pair of line conductors in first and second regions, the first pair of line conductors including a first true line conductor and a first associated complementary line conductor connected and vertically twisted in a vertical twisting region between the first and second regions. The interconnection array subunit also includes a second pair of line conductors adjacent to the first pair of line conductors in the first and second regions, the second pair of line conductors including a second true line conductor and a second associated complementary line conductor. The interconnection array subunit also includes a first interconnection layer disposed in the vertical twisting region, the first interconnection layer connecting the second associated complementary line conductor in the first region to the second associated complementary line conductor in the second region. The interconnection array subunit also includes a second interconnection layer disposed in the vertical twisting region, the second interconnection layer connecting the second true line conductor in the first region to the second true line conductor in the second region. The first true line conductor is disposed below the first associated complementary line conductor in the first region and above the first associated complementary line conductor in the second region. The second true line conductor is disposed below the second associated complementary line conductor in the first and second regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/567,673, filed May 9, 2000, which is incorporated herein by referencein its entirety and to which priority is claimed.

FIELD OF THE INVENTION

This invention relates generally to a semiconductor memory array andsemiconductor integrated circuits, and, more particularly to a schemefor arranging line conductors and interconnection lines in such asemiconductor memory array and in semiconductor integrated circuits.

BACKGROUND OF THE INVENTION

Semiconductor integrated circuits (ICs) typically are formed bymetal-oxide semiconductor (MOS) or bipolar transistors that areintegrated at a planar major surface of a silicon chip. Electricalinterconnections between various transistors, and between certaintransistors and input/output pads, have taken the form of electricallyconnecting lines that comprise a layer of metallization running along anessentially planar surface. In some ICs, two or more “levels” ofinterconnections may be required. The planar surfaces of theinterconnections are oriented mutually parallel to, and are insulatedfrom, both each other and the top planar surface of the chip by suitableinsulating layers. Connections to the transistors at lower levels thanthe metallization layers are provided through openings called contacts,and connections between different interconnection layers are providedthrough insulation openings called vias.

In memory ICs, such as random access memories (RAMs), the data in thememory array are accessed by an external data path by means of a numberof electrically conducting lines. The electrically conducting lines inthe array are conventionally arranged in the form of an array ofparallel metallization strips. For example, a dynamic RAM (DRAM)contains an array of hundreds of parallel bit lines, or digit lines. ADRAM also contains an array of parallel word lines. The word linestypically lie at a different planar level than the bit lines. The arrayof bit lines and the array of word lines lie perpendicular to eachother, forming a grid. Memory cells in the DRAM lie at an intersectionof a bit line and a word line.

The bit lines, or digit lines, in a DRAM can give rise to electricalcross-coupling or “cross-talk.” For example, access to any given bitline or digit line may spuriously influence memory cells connected toadjacent bit lines or digit lines. The term “pattern sensitivity” isapplied to this undesirable phenomenon. The problems of cross-talk andpattern sensitivity can arise in other interconnection arrays, such asaddress busses and data busses where similarly paired, parallellydisposed line conductors are employed. In these environments, cross-talkand pattern sensitivity can result in undesirable errors.

Memory ICs such as DRAMs typically have a memory array of millions ofmemory cells that store electrical charges indicative of binary data.For instance, the presence of an electrical charge in the memory cellusually equates to a binary “1” value, and the absence of an electricalcharge usually equates to a binary “0” value. The memory cells areaccessed via address signals on row and column lines. Once accessed,data is written to, or read from, the addressed memory cell via bitlines, or digit lines.

One common design found in many memory circuit topologies orconfigurations or layouts is the “folded bit line” or “folded digitline” structure or architecture, also known as the 8F² architecture. Ina folded bit line construction, the bit lines are arranged in pairs witheach pair being assigned to complementary binary signals. For example,one bit line (the “true” line) in the pair is dedicated to a binarysignal DATA while the other bit line (the “associated complementary”line) in the pair is dedicated to handle the associated complementarybinary signal DATA*. (The asterisk notation “*” is used throughout toindicate the binary complement.)

The memory cells are connected to one of the bit lines in the foldedpair. During read and write operations, the bit lines are driven toopposing voltage levels depending on the data content being written toor read from the memory cell. For purposes of explanation, the followingexample describes a read operation of a memory cell holding a chargeindicative of a binary “1” value. The voltage potential of both bitlines in the pair are first preferably equalized to a middle voltagelevel such as 1.2V for a memory circuit with a supply voltage level of2.5V. Then, the addressed memory cell is accessed and the charge heldtherein begins to flow to one of the bit lines in the bit line pair,causing the voltage of that bit line to be raised slightly above thevoltage of the other bit line of the pair. A sense amplifier, or similarcircuit, senses the voltage differential on the bit line pair andfurther increases this differential by increasing the voltage on thefirst bit line to 2.5V and decreasing the voltage on the second bit lineto 0 V. The folded bit lines thereby output the data in a complementaryform, which is transmitted to the output pads.

One version of a folded bit line architecture or structure is thetwisted bit line structure. FIG. 1 illustrates a conventional twistedbit line structure having bit line pairs D0/D0* through D3/D3*. Twistingoccurs at twist junctions 120 across the array of bit lines when thetrue line in a bit line pair (D0 for example) exchanges positions withthe associated complementary line (D0*) in the pair. Memory cells arecoupled to the bit line pairs throughout the array. Representativememory cells 122 a through 122 n and 124 a through 124 n are showncoupled to bit line pair D0/D0*. The twisted bit line structure evolvedas a technique to reduce bit line interference noise or cross-talk orpattern sensitivity during chip operation. Such noise becomes moreproblematic as memory density increases. The twisted bit line structureis therefore used in larger, higher density, memories such as a 64 MbDRAM.

Conventional twisted bit line architectures have a number ofdisadvantages as compared to open bit line architectures. Onedisadvantage is the relatively large amount of chip “real estate” thatis typically used by the twist junctions 120. Yet another disadvantageis that the use of the conventional twisted folded bit line architecturemay result in an inefficient use of the cell matrix space. Theconventional twisted bit line architecture does not use spaceefficiently because it provides a lower packing density of memory cellsthan the open bit line architecture, and because it cannot utilize across-point layout cell structure. Some of these disadvantages could beovercome if a cross-point layout were combined with a folded bit linearchitecture. This combination would offer both high packing density andgood noise immunity. Implementing this combination would require thatthe bit lines be vertically twisted, not just horizontally twisted asshown in FIG. 1.

One attempt in the prior art to provide a DRAM architecture thatutilizes the advantages of both a cross-point layout cell architectureand a folded bit line architecture is described in U.S. Pat. No.5,107,459 to Chu et al. Chu utilizes a three-dimensional approach bystacking the two lines in a bit line pair (the true bit line and thecomplementary bit line) vertically one above the other in two layers ofmetallization. The two layers are twisted by means of a third layer.

A scheme similar to the scheme described by Chu is shown conceptuallyand schematically in FIG. 2. In the scheme in FIG. 2, bit line pairs(D₁, D₁*) and (D₂, D₂*) form a sub-array 200. Bit line pair (D₁, D₁*)consists of bit lines D_(1L) and D_(1L)* to the left of the twistingregion 210, and bit lines D_(1R) and D_(1R)* to the right of thetwisting region 210. Similarly, bit line pair (D₂, D₂*) consists of bitlines D_(2L) and D_(2L)* to the left of the twisting region 210, and bitlines D_(2R) and D_(2R)* to the right of the twisting region 210. Thethick strips in FIG. 2 represent a first layer of metallization, and thethin solid lines represent a second layer of metallization arrangedabove, and insulated from, the first layer of metallization. Thealternating dashed-dotted lines in FIG. 2 represent a thirdinterconnection layer, a polysilicon layer, arranged below and insulatedfrom the first layer of metallization. The twisting region 210 issituated between two dummy word lines 220 formed in the polysiliconlayer. The two dummy word lines 220 are situated adjacent to real wordlines (not shown).

In the scheme shown in FIG. 2, the two bit lines (the true bit line andthe complementary bit line) in a bit line pair, which are stackedvertically one above the other, exchange vertical positions as theycross the twisting region 210. In other words, the bit lines arevertically twisted within the twisting region 210. For example, theportion of the true bit line D₂ on the left of the twisting region 210(D_(2L)) is formed in the first (lower) layer of metallization, whilethe portion of D₂ on the right of the twisting region 210 (D_(2R)) isformed in the second (upper) layer of metallization. Likewise, theportion of the complementary bit line D₂* on the left of the twistingregion 210 (D_(2L)*) is formed in the second (upper) layer ofmetallization, while the portion of D₂* on the right of the twistingregion 210 (D_(2R)*) is formed in the first (lower) layer ofmetallization. Thus D₂ and D₂* exchange vertical positions as they crossthe twisting region 210. As shown in FIG. 2, the vertical twisting ofbit line pair (D₂, D₂*) is effected within the twisting region 210 byhaving the bit line D_(2L) veer to its left (upwards in FIG. 2), andconnecting D_(2L) to D_(2R) through a via 230. The vertical twisting ofbit line pair (D₂, D₂*) is further effected within the twisting region210 by having the bit line D_(2R)* veer to its left (downwards in FIG.2), and connecting D_(2R)* to the bit line D_(2L)* through a via 240.

Vertical twisting of the other bit line pair (D₁, D₁*) in sub-array 200is accomplished in a different manner. The portion of the true bit lineD₁ on the left of the twisting region 210 (DIL) is formed in the first(lower) layer of metallization, while the portion of D₁ on the right ofthe twisting region 210 (DIR) is formed in the second (upper) layer ofmetallization. Likewise, the portion of the complementary bit line D₁*on the left of the twisting region 210 (D_(1L)*) is formed in the second(upper) layer of metallization, while the portion of D₁* on the right ofthe twisting region 210 (D_(1R)*) is formed in the first (lower) layerof metallization. As shown in FIG. 2, the vertical twisting of bit linepair (D₁, D₁*) is effected within the twisting region 210 by having thebit line DIL connect to a polysilicon layer interconnection 250 througha contact hole 255. The polysilicon layer interconnection 250 extendsacross the twisting region 210, passes underneath bit lines D_(2L) andD_(2R)*, and connects to an interlayer interconnection 260 through acontact hole 265. The interlayer interconnection 260, which is formed inthe first metallization layer, connects in turn to the bit line DIRthrough a via 270. The vertical twisting of bit line pair (D₁, D₁*) isfurther effected within the twisting region 210 by having the bit lineD_(1R)* connect to a polysilicon layer interconnection 275 through acontact hole 280. The polysilicon layer interconnection 275 extendsacross the twisting region 210, passes underneath the bit lines D_(2R)*and D_(2L), and connects to an interlayer interconnection 285 through acontact hole 290. The interlayer interconnection 285, which is formed inthe first metallization layer, connects in turn to the bit line D_(1L)*through a via 295.

The vertical twisting scheme represented in FIG. 2 has a number ofshortcomings. One shortcoming is that the bit line pairs within eachsub-array exchange horizontal positions as they cross the twistingregion 210. In other words, the bit lines are twisted horizontally aswell as vertically. For example, bit line pairs (D₁, D₁*) and (D₂, D₂*)in FIG. 2 exchange horizontal positions (upper and lower positions inthe figure) within sub-array 200 as they cross the twisting region 210.This exchange of horizontal positions tends to complicate the layout ofthe memory array. Another shortcoming of the scheme in FIG. 2 is thatthe scheme requires the use of two sets of polysilicon layerinterconnections to effect the vertical twisting of the odd-numbered bitline pairs, (D_(2j+1), D_(2j+1)*) (with j=0, 1, 2, 3) in each sub-array.For example, in FIG. 2 two polysilicon layer interconnections (250 and275) are used to effect the vertical twisting of the odd-numbered bitline pair (D₁, D₁*) in sub-array 200. A third shortcoming of thevertical twisting scheme in FIG. 2 is that the scheme requires threelayers to achieve the twist. This added complexity takes up more space(being both wide and long due to additional metal pads) and does notallow three twists. Further, the vertical twisting scheme of FIG. 2requires the deposition of additional layers beyond the layers depositedin the standard DRAM fabrication process. A final shortcoming of thescheme in FIG. 2 is that the scheme does not allow vertical twisting ofonly one of the bit line pairs of each sub-array. A twisting schemewithout this shortcoming would provide more design flexibility. Forexample, the ability to effect vertical twisting of only one of the bitline pairs would allow the twisting of each of the bit line pairs in asub-array 200 to occur at different locations, as shown in FIG. 1 (wherebit line pair (D0, D0*) is twisted at a different location 120 than bitline pair (D1, D1*)). Staggering the locations at which adjacent bitline pairs are twisted provides superior noise reduction.

The present invention is directed to overcoming, or at least reducingthe effects of, one or more of the perceived shortcomings of prior arttwisting schemes. Furthermore, the present invention advantageouslyoccupies less chip “real estate” than the vertical twisting schemerepresented in FIG. 2.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, aninterconnection array subunit and method for forming the interconnectionarray subunit are provided, the interconnection array subunit includinga first pair of line conductors in first and second regions, the firstpair of line conductors including a first true line conductor and afirst associated complementary line conductor connected and verticallytwisted in a vertical twisting region between the first and secondregions. The interconnection array subunit also includes a second pairof line conductors adjacent to the first pair of line conductors in thefirst and second regions, the second pair of line conductors including asecond true line conductor and a second associated complementary lineconductor. The interconnection array subunit also includes a firstinterconnection layer disposed in the vertical twisting region, thefirst interconnection layer connecting the second associatedcomplementary line conductor in the first region to the secondassociated complementary line conductor in the second region. Theinterconnection array subunit also includes a second interconnectionlayer disposed in the vertical twisting region, the secondinterconnection layer connecting the second true line conductor in thefirst region to the second true line conductor in the second region. Thetwo interconnection layers do so by bypassing beneath the adjacent twistregion. The first true line conductor is disposed below the firstassociated complementary line conductor in the first region and abovethe first associated complementary line conductor in the second region.The second true line conductor is disposed below the second associatedcomplementary line conductor in the first and second regions.

In accordance with another aspect of the instant invention, a method isprovided for laying out line conductors for such an interconnectionarray subunit.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description of a specific embodiment ofthe invention, and upon reference to the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic circuit topology having a conventional foldedand twisted bit line structure;

FIG. 2 is a schematic diagram of a conventional stacked bit linearchitecture;

FIG. 3 is a schematic diagram of a stacked digit line architectureaccording to an embodiment of the present invention;

FIG. 4 is a digit line layout view of a vertical twisting regionaccording to the embodiment shown in FIG. 3;

FIG. 5 is a cross-sectional view of the view of FIG. 4 taken along theline V-V;

FIG. 6 is a cross-sectional view of the view of FIG. 4 taken along theline VI-VI;

FIG. 7 is a cross-sectional view of the view of FIG. 4 taken along theline VII-VII; and

FIG. 8 is a cross-sectional view of the view of FIG. 4 taken along theline VIII-VIII.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, that will vary from one implementation toanother. Moreover, it will be appreciated that such a developmenteffort, even if complex and time-consuming, would be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

Turning now to the drawings, and in particular to FIG. 3, aninterconnection array is shown conceptually and schematically for oneparticular embodiment of the invention. The interconnection arrayconsists of a series of adjacent interconnection array subunits 300.Each interconnection array subunit 300 comprises two adjacent bit linepairs, which are also known as digit line pairs. For example, thetopmost interconnection array subunit 300 in FIG. 3 comprises digit linepairs (D₁, D₁*) and (D₂, D₂*). The interconnection array in FIG. 3comprises a total of ten digit line pairs, (D_(i), D_(i)*) (with i=1, 2,. . . 10), in five interconnection array subunits 300. Eachinterconnection array subunit 300 includes two consecutively numbereddigit bit line pairs. One of the consecutively numbered pairs is anodd-numbered digit line pair, (D_(2j+1R),D_(2j+1R)*) (j=0, 1, 2, 3, 4),and the other pair is an even-numbered digit bit line pair,(D_(2k),D_(2k)*) (k=1, 2, 3, 4, 5).

The interconnection array also contains a vertical twisting region 310,which is situated between two dummy word lines 320. The interconnectionarray can be considered to consist of three regions: the region to theleft of the twisting region 310, the twisting region 310, and the regionto the right of the twisting region 310. The portions of the digit linesin each digit line pair, (D_(i), D_(i)*) (with i=1, 2, . . . 8), in theregion to the left of the twisting region 310 are designated D_(iL) andD_(iL)*, while the portions of the digit lines in the region to theright of the twisting region 310 are designated D_(iR) and D_(iR)*. Thedigit lines within each digit line pair are separated by a digit linepitch P.

In the embodiment in FIG. 3, the digit lines D_(iL) are interconnectionsformed in a buried layer of polycide, while the digit lines D_(iL)* areinterconnections formed in a layer of metallization. As best seen inFIG. 5, the digit lines formed in a layer of metallization are arrangedabove, and insulated from, the digit lines formed in a buried layer ofpolycide. In FIG. 3, digit lines formed in a buried layer of polycide,such as D_(1L), are represented as thick strips, whereas digit linesformed in a layer of metallization, such as D_(1L)*, are represented asthin solid lines.

The alternating dashed-dotted lines of FIG. 3 representinterconnections, such as interconnection 350, are formed in apolysilicon layer. As best shown in FIGS. 6 and 7, interconnectionsformed in the polysilicon layer are arranged below, and insulated from,the buried layer of polycide (D_(5L) and D_(5R)* in FIG. 6, and D_(8L)and D_(8R) in FIG. 7). The dotted lines in FIG. 3 representinterconnections, such as interconnection 370, that are formed in anactive area layer. As best shown in FIGS. 5 and 6, interconnectionsformed in an active area layer, such as interconnection 370, arediffused into an underlying substrate, such as substrate 500. As alsoshown in FIG. 6, an active area layer, such as interconnection 370, maybe arranged so it does not lie beneath the interconnections formed inthe polysilicon layer, such as interconnection 350. In this arrangement,the polysilicon interconnection 350 does not overlap the active arealayer interconnection 370. Alternatively, active area layerinterconnections may be arranged below, and insulated from,interconnections formed in the polysilicon layer. The active area layermay also be arranged beneath, and insulated from, the buried layer ofpolycide. For example, in FIG. 5 the active area layer 370 is beneath,and insulated from, buried polycide layers D_(1L) and D_(1R)*.

In the interconnection array shown in FIG. 3, only the odd-numbereddigit lines pairs are vertically twisted within the vertical twistingregion 310. This is similar to the portion of the array in the left-mostthird of FIG. 1, where only odd bit line pairs (D1, D1*) and D3, D3*)are twisted. In the region to the left of the vertical twisting region310 all true digit lines, including the true odd digit lines D_(2j+1L)(j=0, 1, 2, 3, 4), are formed in the buried layer of polycide. In thissame region, all of the associated complementary digit lines, includingthe associated complementary odd digit lines D_(2j+1L)* (j=0, 1, 2, 3,4), are formed in the layer of metallization. In the region to the rightof the vertical twisting region 310, after vertical twisting, the trueodd digit lines D_(2j+1R) (j=0, 1, 2, 3, 4) are formed in the layer ofmetallization and the associated complementary odd digit linesD_(2j+1R)* (j=0, 1, 2, 3, 4) are formed in the buried layer of polycide.Thus both the true odd digit lines and the associated complementary odddigit lines have been vertically twisted in the vertical twisting region310.

The vertical twisting of the odd digit line pairs (D_(2j+1), D_(2j+1)*)(j=0, 1, 2, 3, 4) is effected in the vertical twisting region 310 byhaving the true odd digit lines, D_(2j+1L) (j=0, 1, 2, 3, 4), connect totheir respective true odd digit lines to the right of the twistingregion 310, D_(2j+1R) (j=0, 1, 2, 3, 4), through contact holes 330 and340. As shown in FIG. 6, the contact hole 330 connects a buried polycidetrue odd digit line in the region to the left of the twisting region 310(D_(5L) in FIG. 6) to a metallization true odd digit line in the regionto the right of the twisting region 310 (D_(5R) in FIG. 6).

The vertical twisting of the odd digit line pairs is further effected byhaving the associated complementary digit lines in the region to theleft of the twisting region 310, D_(2j+1L)* (j=0, 1, 2, 3, 4), connectto their respective associated complementary digit lines in the regionto the right of the twisting region, D_(2j+1R)* (j=0, 1, 2, 3, 4). Thisconnection takes place through contact holes 340, as shown in FIGS. 3and 5.

In contrast to the odd-numbered digit lines pairs, the even-numbereddigit line pairs (D_(2k), D_(2k)*) (k=1, 2, 3, 4) are not verticallytwisted within the vertical twisting region 310. As shown in FIG. 3, inthe region to the left of the vertical twisting region 310 the true evendigit lines D_(2kL) (k=1, 2, 3, 4) are formed in the buried layer ofpolycide, and the associated complementary digit lines D_(2kL)* (k=1, 2,3, 4) are formed in the layer of metallization. In the region to theright of the vertical twisting region 310, true even digit lines D_(2kR)(k=1, 2, 3, 4) are formed in the buried layer of polycide, and theassociated complementary digit lines D_(2kR)* (k=1, 2, 3, 4) are formedin the layer of metallization.

As shown in FIGS. 3 and 7, interconnection of the even digit line pairs(D_(2k), D_(2k)*) (k=1, 2, 3, 4) across the vertical twisting region 310is effected, without vertical twisting, by having the associatedcomplementary digit lines D_(2kL)* (k=1, 2, 3, 4) connect tointerconnections 350 in the polysilicon layer through contact holes 355.The interconnections 350 in the polysilicon layer extend across thevertical twisting region 310, pass underneath the true odd digit linesD_(2j+1L) and D_(2j+1R) (j=0, 1, 2, 3), and connect to respectiveassociated complementary digit lines D_(2kR)* (k=1, 2, 3, 4) throughcontact holes 360.

As shown in FIGS. 3 and 8, the interconnection of the even digit linepairs across the vertical twisting region 310 is further effected,without vertical twisting, by having the true even digit lines D_(2kL)(k=1, 2, 3, 4) connect to interconnections 370 in the active layerthrough a buried contact or plug contact 375. The active areainterconnection 370 also contacts the material 700 within the contacthole 375. As shown in FIG. 8, the active area interconnection 370extends from the contact 375 across the vertical twisting region 310,passing underneath all other interconnection layers, and connects to atrue even digit lines (D_(10R) in FIG. 8) through a contact 380. Aspreviously discussed, the contact between the true even digit line(D_(10R)) and the material 710 in the contact hole 380 may be in theform of a plug contact.

In the interconnection array in FIG. 3, the odd digit line pairs(D_(2j+1), D_(2j+1)*) (j=0, 1, 2, 3) are vertically twisted, while theeven digit line pairs (D_(2k), D_(2k)*) (k=1, 2, 3, 4) are not twisted.In other interconnection arrays in the same memory array, the even digitlines pairs may be vertically twisted, while the odd digit line pairsare not twisted. By twisting the even digit line pairs and the odd digitline pairs in adjacent interconnection arrays, the location of thetwisting regions 310 for even and odd digit line pairs can be staggered.FIG. 1 shows a similar staggering of the twisting regions 120 for oddand even digit line pairs. The twisting regions for the even and odddigit line pairs must be staggered in order to provide effective noisecancellation.

The vertical twisting scheme implemented in the interconnection array inFIG. 3 has a number of advantages over the conventional verticaltwisting scheme shown in FIG. 2. The scheme in FIG. 3 employs only asingle polysilicon interconnection layer and an active region 350, whichis deposited as a matter of course in the standard DRAM fabricationprocess. The conventional vertical twisting scheme in FIG. 2 requiresthe deposition of a second polysilicon interconnection layer that is notdeposited in the standard DRAM fabrication process. Furthermore, thescheme in FIG. 3 vertically twists the odd digit line pairs, (D_(2j+1),D_(2j+1)*) (j=0, 1, 2, 3) without vertically twisting the even digitline pairs (D_(2k), D_(2k)*) (k=1, 2, 3, 4). The scheme in FIG. 3 doesnot transpose the horizontal locations of the digit line pairs within aninterconnection array subunit 300, such as the subunit containing digitline pairs (D₁, D₁*) and (D₂, D₂*). Conversely, the vertical twistscheme in FIG. 2 transposes the horizontal location of the bit lines inthe bit line pair in each sub-array 200, such as the sub-arraycontaining bit line pairs (D₁, D₁*) and (D₂, D₂*). Also, the verticaltwist scheme of FIG. 3 does not require pads 260 and 290.

FIG. 4 illustrates how the embodiment shown schematically in FIG. 3 maybe physically laid out on an IC. The view of the interconnection arrayin FIG. 4 shows eleven digit line pairs, (D_(i), D_(i)*) (i=1, 2, . . .11), and five interconnection array subunits 300. The portions of thedigit lines in the region to the left of the vertical twisting region310 are designated D_(iL) and D_(iL)*, and the portions of the digitlines in the region to the right of the vertical twisting region 310 aredesignated D_(iR) and D_(iR)*. The separation between the digit lines ineach digit line pair is the digit line pitch P.

In FIG. 4, each of the interconnection layers in the interconnectionarray is represented by a different pattern. Interconnections formed inthe buried layer of polycide, which are represented by the thick stripsin FIG. 3, are represented in FIG. 4 by thick strips containing sparsediagonal hatching. Interconnections formed in the layer ofmetallization, which were represented by solid lines in FIG. 3, arerepresented by the thinner strips with denser hatching in FIG. 4.Interconnections formed in the polysilicon layer, which are representedby alternating dashed-dotted lines in FIG. 3, are represented by stripsfilled with circles in FIG. 4. Finally, interconnections formed in theactive area layer, which are represented by dotted lines in FIG. 3, arerepresented in FIG. 4 by strips containing dots.

FIG. 4 also shows the physical layout of the contacts in theinterconnection array. The contacts that provide a pathway from ametallization interconnection layer down to a buried polycideinterconnection layer are represented by solid black squares. This typeof contact provides pathways between true odd digit lines on the left ofthe twisting region 310 D_(2j+1L) (j=0, 1, 2, 3, 4, 5), which are formedin buried polycide, to their respective true odd digit lines on theright of the twisting region 310 D_(2j+1R) (j=0, 1, 2, 3, 4, 5), whichare formed in the metallization layer. This type of contact alsoprovides pathways between associated complementary odd digit lines onthe left of the twisting region 310 D_(2j+1L)* (j=0, 1, 2, 3, 4, 5),which are formed in the metallization layer, to their respectiveassociated complementary odd digit lines on the right of the twistingregion 310 D_(2j+1R)* (j=0, 1, 2, 3, 4, 5), which are formed in theburied polycide layer.

In the physical layout shown in FIG. 4, the contacts drop down onto anenlarged portion of the buried polycide. This enlarged portion isreferred to as a surround. So FIG. 4 shows contact holes 330 and 340contacting surrounds 430 and 440 respectively. The enlarged size of thesurrounds helps ensure the contact holes (330,340) will contact theburied polycide layer (430,440), even if there is a slight misalignmentof the masks defining the location of the buried polycideinterconnection layer and the mask defining the location of the contacthole (330,340).

FIG. 4 also shows the contacts that provide a pathway between aninterconnection formed in the metallization layer and an interconnectionformed in the polysilicon. These contacts are represented by solid blacksquares crossed by the diagonals of larger circumscribing squares. Thelarger circumscribing square is only intended to differentiate between acontact between metallization and polysilicon layers from a contactbetween metallization and buried polycide layers. The circumscribingsquare does not imply that contacts between via between metallizationand polysilicon layer must be larger in size. As shown in FIGS. 3, 4,and 7, contacts 355 between metallization and polysilicon layers connectthe associated complementary even digit lines to the left of thetwisting region 310 D_(2kL)* (k=1, 2, 3, 4, 5) to the polysiliconinterconnection 350. The contact 355 contacts the polysilicon layer withsurround 455. Similarly, FIGS. 3, 4, and 7 show that contacts 360between metallization and polysilicon layers connect the even associatedcomplementary digit lines D_(2kR)* (k=1, 2, 3, 4, 5) to polysiliconinterconnection layer 350. A surround 460 is included in the polysiliconinterconnection layer 350.

FIG. 4 also shows the contacts that provide a pathway between aninterconnection formed in the buried polycide layer and aninterconnection formed in the active area. The contacts are representedby cross-hatched rectangles. The digit line is shown as partiallycovering the contact in this embodiment, but the layout could be alteredsuch that the digit line completely covers the contact. In the layoutshown in FIG. 4, the contacts (375, 380) provide a pathway between trueeven digit lines, D_(2kL) (k=1, 2, 3, 4, 5) and D_(2kR) (k=1, 2, 3, 4,5) respectively, and the active area interconnection layer 370.

FIG. 4 shows that some of the interconnection layers may lie directlyunder other layers, including those that form digit lines. As shown inthe cross-sectional views in FIGS. 5 through 8, an interconnection layermay underlie another layer as long as there is an insulating layerseparating the layers. For example, the active area interconnectionlayer (e.g. 370 in FIGS. 6 and 8) may lie directly under the digit linesformed in the buried polycide interconnection layer (e.g. D_(5L) in FIG.6 and D_(11L) in FIG. 8) since an insulating layer 510 separates theinterconnection layers. The active area interconnection layer (e.g. 370in FIGS. 6 and 8) may also lie directly under interconnection layersformed in the metallization layer (e.g. D_(5R) in FIG. 6 and D_(11L)* inFIG. 8) since the interconnection layers are separated by thecombination of insulating layers 510 and 520. Interconnections formed inthe buried polycide layer (e.g. D_(5L) in FIG. 6 and D_(11L) in FIG. 8)may in turn lie directly under interconnections formed in themetallization layer (e.g. D_(5L)* in FIG. 6 and D_(11L)* in FIG. 8)since those interconnection levels are separated by insulating layer520. The only exception is that interconnections formed in thepolysilicon layer (e.g. 350 in FIG. 6) may not overlie theinterconnections formed in the active area (e.g. 370 in FIG. 6) becausethe active area is implanted into the substrate 500 after thepolysilicon layer has been deposited. Insulating layers 510 and 520 maybe formed of silicon oxide or the like, and each layer may be formed inone or more processing steps.

FIG. 5 is a schematic cross-sectional view taken along the line V-V inFIG. 4. This line traverses the top row in an interconnection arraysubunit 300. FIG. 5 shows that the interconnection 370 in the activearea may be formed in a diffused region in a semiconductor substrate500, such as a P-well, with the substrate 500 doped so as to have aP-type conductivity, for example. The interconnection 370 in the activearea may then be doped so as to have an N⁺-type conductivity. Thesubstrate 500 may have an upper surface 530. An insulating layer 510insulates the interconnection 370 in the active area from the burieddigit lines. The insulating layer 510 also insulates the dummy wordlines 320 from the true digit line D_(1L) and the associatedcomplementary digit line D_(1R)*, which are both formed in the buriedlayer of polycide. An insulating layer 520 insulates the true digit lineD_(1L) and the associated complementary digit line D_(1R)*, which areboth formed in the buried layer of polycide, from the associatedcomplementary digit line D_(1L)* and the true digit line D_(1R), whichare both formed in the layer of metallization. The associatedcomplementary digit line D_(1L)* connects to the respective associatedcomplementary digit line D_(1R)* through the contact 340, which contactsthe buried polycide layer forming D_(1R)* within the surround 440. Asuitable plug, such as a tungsten plug, may be used to form contact 340.

Turning now to FIG. 6, a schematic cross-sectional view taken along theline VI-VI in FIG. 4. This line traverses the path of a true odd digitline, including portions D_(2j+1L) and D_(2j+1R) (j=0, 1, 2, 3, 4, 5).This path crosses three sections of active area interconnection 370. Themiddle section of active area interconnection 370 in FIG. 6 is theinterconnection 370 formed in the active area between the digit linepairs (D₆, D₆*) and (D₇, D₇*), and which connects D_(6L) to D_(6R)*. Theside sections of the interconnection 370, on either side of the middlesection of the interconnection 370, are formed in the active areabetween the digit line pairs (D₄, D₄*) and (D₅, D₅*), and connect D_(4L)to D_(4R)*. Two sections of polysilicon interconnection 350 are shown inFIG. 6. Both sections are formed in the polysilicon layer between thedigit line pairs (D₅, D₅*) and (D₆, D₆*) that connects D_(6L)* toD_(6R)*. As can be seen in FIG. 6, active area 370 is insulated fromother interconnects.

The insulating layer 510 also insulates the dummy word lines 320 and theinterconnection 350 from the true digit line D_(5L) and the associatedcomplementary digit line D_(5R)*, both formed in the buried layer ofpolycide. The insulating layer 520 insulates the true digit line D_(5L)and the associated complementary digit line D_(5R)*, both formed in theburied layer of polycide, from the associated complementary digit lineD_(5L)* and the true digit line D_(5R), both formed in the layer ofmetallization. The true digit line D_(5L) connects to the respectivetrue digit line D_(5R) through the contact hole 330, which is surroundedby the surround 430. A suitable plug, such as an aluminum plug or atungsten plug, may be used to fill the contact hole 330.

FIG. 7 shows a schematic cross-sectional view taken along the lineVII-VII in FIG. 4. This line traverses the path of an associatedcomplementary even digit line, including portions D_(2jL)* and D_(2jR)*(j=1, 2, 3, 4, 5). The path crosses a section of true odd digit line(D_(7L)) with surround 430, a section of associated complementary odddigit line (D_(7L)*) with surround 440, and a section of true odd digitline (D_(7R)), all of which are insulated from each other by theinsulating layer 520. The insulating layer 510 insulates theinterconnection 350 from the true even digit lines D_(8L) and D_(8R),which are both formed in the buried layer of polycide. The insulatinglayer 520, in turn, insulates the true even digit lines D_(8L) andD_(8R), which are both formed in the buried layer of polycide, from theassociated complementary digit lines D_(8L)* and D_(8R)*, both formed inthe layer of metallization. The associated complementary even digit lineD_(8L)* connects to the interconnection 350 formed in the polysiliconlayer through the contact hole 355, which is surrounded by the surround455.

The polysilicon interconnection layer 350 connects, in turn, to thecorresponding associated complementary digit line D_(8R)* through thecontact hole 360, which is surrounded by the surround 460. A suitableplug, such as an aluminum or a tungsten plug, may be used to fill thecontact holes 355 and 360. Also shown in FIG. 7 is a section of thecontact hole 375, filled with a polysilicon plug 700, and a section ofthe contact hole 380, filled with a polysilicon plug 710. As shown inFIGS. 7 and 8, the polysilicon plugs 700 and 710 connect the true digitlines (e.g. D_(8L) and D_(8R)) to the upper surface 530 of the substrate500.

FIG. 8 shows a schematic cross-sectional view taken along the lineVIII-VIII in FIG. 4. This line traverses the path taken by a true evenbit line. The path crosses sections of digit line pairs (D₁₁, D₁₁*), asection of digit line D_(9L) with surround 430, and a section ofassociated complementary digit line D_(11R)* with surround 440, allinsulated from each other by the insulating layer 520, and all insulatedfrom the interconnection 370 in the active area by the insulating layer510. The insulating layer 520, in turn, insulates the true digit linesD_(10L) and D_(10R), both formed in the buried layer of polycide, fromthe associated complementary digit lines D_(10L)* and D_(10R)*, bothformed in the layer of metallization. The true digit line D_(10L)connects to the interconnection 370 formed in the active area throughthe contact hole 375. The interconnection 370 formed in the active areaconnects, in turn, to the respective true digit line D_(10R) throughcontact 380. Contacts 375 and 380 may be filled with the polysiliconplugs 700 and 710, respectively, as shown in FIGS. 7 and 8.

The fabrication of embodiments of the present invention involve a numberof process steps. These steps are typically inherent to a DRAM processand no special steps are required except in some cases. A first stepincludes forming a p-well in a semiconductor substrate such as a siliconsubstrate, which will hold the DRAM array. A second step includesforming active areas and field isolation regions. A third step includesforming n-well regions in which the p-channel devices will be formed. Afourth step includes forming a first insulating layer on the activeareas to act as gate oxide layers for transfer transistors. A fifth stepincludes forming and patterning a polysilicon/tungsten silicide/capoxide stack (also referred to as polysilicon or poly) on the firstinsulating layer to act as gate electrodes for the transfer transistors,word lines and also form interconnections 350 in the vertical twistingregion 310.

Next, sidewall spacers are formed on the polysilicon gates, and then-channel and p-channel transistors are formed by masking andimplantation according to the CMOS process employed. A barrier oxidelayer (300 A or so) is then deposited followed by Borophosphsilicateglass (BPSG) deposition. This is planarized, using, for example,chemical-mechanical polishing (CMP) techniques known to those ofordinary skill in the art to provide a planarized surface for subsequentprocessing. Contact holes are then formed in the BPSG layers, theseholes then being filled with conductive plugs of, for example, heavilyn-type polysilicon. These plugs are used in the array to contact thecell capacitors and in the twist region to form contacts between theburied digit line and active area. They could also be employed tocontact the n-channel transistors in the periphery.

The next step involves deposition of a thin (e.g., 500 Å) oxide (TEOS)layer, and patterning that layer using conventional mask techniques toopen up holes therein through to the plugs desired to be contacted,including those in the twist where a contact between the buried digitline and active area needs to be formed

Another polysilicon/tungsten silicide/cap oxide stack is deposited andpatterned to form the buried digit lines. After this is accomplished,the DRAM capacitors are formed on top of the digit lines, in aconventional manner.

After capacitor formation, another layer of BPSG is deposited andplanarized as previously described. The BPSG layer is then patterned toform contacts to active areas, polysilicon plugs or buried digit linesbelow, including contacts in the twist region where the buried digitline is to be twisted up to metal 1 and metal 1 twisted down to burieddigit line. The contacts are then filled with plugs of, for example,tungsten after a barrier layer such as TiN has been deposited. ChemicalVapor Deposition (CVD) is typically used for these steps. Next the metal1 is formed and patterned. The metal 1 in a typical embodiment comprisesa 300 A Ti/3 kA AlCu/300 A TiN stack. It is used to form interconnectsfor the circuits, route power supplies and form the complementary digitlines. At this point, the processing completes the formation of thevertical twist. The remaining steps such as metal 2, passivation etc. inthe DRAM processing can be carried out using steps inherent to the DRAMprocess.

The foregoing is not necessarily an exhaustive outline of the processingsteps that may be required to fabricate a memory IC in accordance withan embodiment of this invention. In other words, one skilled in the arthaving the benefit of the present disclosure would recognize that otherprocessing steps may precede, follow, or be interspersed with the thoseoutlined above.

The vertical twist scheme, as described in the embodiment shown in FIGS.3-8, enables a 6F² cross-point architecture for a high-density DRAMmemory array to be realized. The true and associated complementary digitline pairs in such a DRAM memory array are formed in a buried polycideand an overlying metal layer. The twist is achieved vertically betweenthe polycide layer and the metal layer for every twisted digit line pairwithout using an additional underlying interconnection layer and whilemaintaining the column pitch restraints. The column pitch restraints aremaintained by having the adjacent untwisted digit line pair routed underthe vertical twist of the twisted digit line pair by using theunderlying active area and an underlying polysilicon layer asinterconnection layers for the adjacent untwisted digit line pair. Inthis embodiment, not every digit line pair is twisted in each verticaltwisting region. Each twisted digit line pair is adjacent to anuntwisted digit line pair. Further, in this embodiment, adjacent digitline pairs are not transposed across each vertical twisting region.

The vertical twist scheme, as described in the embodiment shown in FIGS.3-8, does not rely on using cell polysilicon, used in memory cellcapacitors, as an interconnection layer for the adjacent untwisted digitline pair, using instead the underlying active area and the underlyingpolysilicon layer, used also for the gate polysilicon, asinterconnection layers for the adjacent untwisted digit line pair,thereby improving the manufacturing yield for such a vertical twist. Theinterconnection formed in the underlying polysilicon layer that is alsoused for the gate polysilicon has a lower sheet resistance (also knownas sheet resistivity) than the cell polysilicon used in memory cellcapacitors, and the gate polysilicon layer is a much better layer toconnect to through a contact hole. The gate polysilicon layer may bepolycided and may have a sheet resistance of about 7-8 ohms per square(Ω/□). The polysilicon layer may be doped, for example, with phosphorus,to render it electrically conductive, and then the polyciding may beaccomplished by depositing either a refractory metal silicide layerdirectly on the polysilicon layer. Those of ordinary skill in the artwill appreciate that the polycided gate can be replaced with arefractory metal gate or refractory metal/polysilicon gate stack.Aluminum or aluminum alloy may be used for the layer of metallization.One of ordinary skill in the integrated circuit fabrication art wouldrecognize that an N-well in a semiconductor substrate such as a siliconsubstrate may be used instead of the P-well, and that P⁺-type diffusionregions may be used for the active areas instead of the N⁺-typediffusion regions.

Although the concepts of the present invention are presented principallyherein in connection with semiconductor memory arrays, they are equallyapplicable to any IC device employing paired line conductors extendingsubstantially parallel to each other. One of ordinary skill in therelevant arts would recognize that the vertical twist scheme, asdescribed in the embodiment shown in FIGS. 3-8, would also be applicableto any interconnection array having paired true/associated complementaryline conductors, such as integrated circuit address/data busses.

The vertical twist scheme, as described in the embodiment shown in FIGS.3-8, also enables more control over the sheet resistances of theinterconnections formed in the underlying gate polysilicon layer and ofthe interconnections formed in the underlying active areas. The N⁺-typediffusion regions for the active areas may have a sheet resistance ofabout 100 Ω/□, and any mismatch between the sheet resistances of theinterconnections formed in the gate polysilicon layer and theinterconnections formed in the active areas may be reduced by wideningthe active area. Those of ordinary skill in the art having the benefitof the present disclosure will appreciate that it may be possible tochoose diffusions or interconnect layers other than as disclosed hereinin the practice of the present invention. For example, in the disclosedembodiment, the active area can be replaced with a polysilicon plug,with no penalty.

Although a specific embodiment of the invention has been disclosedherein in some detail, it is to be understood that this has been donesolely for the purposes of illustrating various features and aspects ofthe present invention, and is not intended to be limiting with respectto the scope of the invention as defined in the appended claims. It iscontemplated that those of ordinary skill in the art having the benefitof this disclosure will be able to make various substitutions,alterations and/or modifications to the disclosed embodiment, includingbut not limited to those implementation-specific alternatives which mayhave been specifically noted in this disclosure, without departing fromthe spirit and scope of the invention.

1. A line conductor layout method for an interconnection array, themethod comprising: forming a plurality of first paired line conductors,each pair including a first true line conductor and a first associatedcomplementary line conductor, the plurality of first paired lineconductors being substantially parallel within a first region and withina second region, each of the first true line conductors being disposedbelow each of the first associated complementary line conductors in thefirst region and each of the first true line conductors being disposedabove each of the first associated complementary line conductors in thesecond region; forming a plurality of second paired line conductors,each pair including a second true line conductor and a second associatedcomplementary line conductor, the plurality of second paired lineconductors being substantially parallel within the first region andwithin the second region, each of the second true line conductors beingdisposed below each of the second associated complementary lineconductors in the first region and in the second region, the pluralityof second paired line conductors alternating with the plurality of firstpaired line conductors so that each pair of the plurality of firstpaired line conductors is adjacent to a corresponding pair of theplurality of second paired line conductors; forming a plurality of firstinterconnection layers disposed in a vertical twisting region betweenthe first region and the second region, each of the firstinterconnection layers connecting a respective second associatedcomplementary line conductor of the plurality of second paired lineconductors in the first region to a corresponding second associatedcomplementary line conductor of the plurality of second paired lineconductors in the second region, the plurality of first interconnectionlayers being disposed below first portions of the plurality of firstpaired line conductors in the vertical twisting region; and forming aplurality of second interconnection layers disposed in the verticaltwisting region, each of the second interconnection layers connecting arespective second true line conductor of the plurality of second pairedline conductors in the first region to a corresponding second true lineconductor of the plurality of second paired line conductors in thesecond region; wherein the plurality of second interconnection layersalternate with the plurality of first interconnection layers such thateach of the first interconnection layers of the plurality of firstinterconnection layers is non-overlapping with a corresponding secondinterconnection layer of the plurality of second interconnection layers;and wherein the plurality of second interconnection layers is disposedbelow second portions of the plurality of first paired line conductorsin the vertical twisting region; and wherein each of the first true lineconductors of the plurality of first paired line conductors in the firstregion is connected in the vertical twisting region to a respectivefirst true line conductor of the plurality of first paired lineconductors in the second region and each of the first associatedcomplementary line conductors of the plurality of first paired lineconductors in the first region is connected in the vertical twistingregion to a respective first associated complementary line conductor ofthe plurality of first paired line conductors in the second region. 2.The method of claim 1, wherein the first and second true line conductorsinclude polycide.
 3. The method of claim 1, wherein the first and secondassociated complementary line conductors include metal.
 4. The method ofclaim 1, wherein the first interconnection layers include polysilicon.5. The method of claim 1, wherein the second interconnection layers areformed to include active areas.
 6. The method of claim 1, wherein afirst pitch between successive first paired line conductors and secondpaired line conductors in the first region is formed to be substantiallysimilar to a second pitch between successive first paired lineconductors and second paired line conductors in the second region. 7.The method of claim 1, wherein each of the first interconnection layersis connected to the respective and corresponding second associatedcomplementary line conductors through respective first and secondcontact holes disposed substantially at respective first and secondperipheral portions of each of the first interconnection layers in thevertical twisting region.
 8. The method of claim 1, wherein each of thesecond interconnection layers is connected to the respective andcorresponding second true line conductors through respective first andsecond overlapping interconnects disposed substantially at respectivefirst and second peripheral portions of each of the secondinterconnection layers in the vertical twisting region.
 9. The method ofclaim 1, wherein each of the first true line conductors of the pluralityof first paired line conductors in the first region is connected to therespective first true line conductor of the plurality of first pairedline conductors in the second region through a third contact hole in thevertical twisting region.
 10. The method of claim 1, wherein each of thefirst associated complementary line conductors of the plurality of firstpaired line conductors in the first region is connected to therespective first associated complementary line conductor of theplurality of first paired line conductors in the second region through afourth contact hole in the vertical twisting region.
 11. The method ofclaim 2, wherein: the first and second associated complementary lineconductors are formed to include metal; the first interconnection layersare formed to include polysilicon and the second interconnection layersare formed to include active areas; a first pitch between successivefirst paired line conductors and second paired line conductors in thefirst region is formed to be substantially similar to a second pitchbetween successive first paired line conductors and second paired lineconductors in the second region; each of the first interconnectionlayers is connected to the respective and corresponding secondassociated complementary line conductors through respective first andsecond contact holes disposed substantially at respective first andsecond peripheral portions of each of the first interconnection layersin the vertical twisting region; each of the first true line conductorsof the plurality of first paired line conductors in the first region isconnected to the respective first true line conductor of the pluralityof first paired line conductors in the second region through a thirdcontact hole in the vertical twisting region; each of the firstassociated complementary line conductors of the plurality of firstpaired line conductors in the first region is connected to therespective first associated complementary line conductor of theplurality of first paired line conductors in the second region through afourth contact hole in the vertical twisting region; and each of thesecond interconnection layers is connected to the respective andcorresponding second true line conductors through respective first andsecond overlapping interconnects disposed substantially at respectivefirst and second peripheral portions of each of the secondinterconnection layers in the vertical twisting region.
 12. A lineconductor layout method for an interconnection array subunit, the methodcomprising: forming a first pair of line conductors in first and secondregions, the first pair of line conductors including a first true lineconductor and a first associated complementary line conductor connectedand vertically twisted in a vertical twisting region between the firstand second regions; forming a second pair of line conductors adjacent tothe first pair of line conductors in the first and second regions, thesecond pair of line conductors including a second true line conductorand a second associated complementary line conductor; forming a firstinterconnection layer disposed in the vertical twisting region, thefirst interconnection layer connecting the second associatedcomplementary line conductor in the first region to the secondassociated complementary line conductor in the second region; andforming a second interconnection layer disposed in the vertical twistingregion, the second interconnection layers connecting the second trueline conductor in the first region to the second true line conductor inthe second region, wherein the first true line conductor is disposedbelow the first associated complementary line conductor in the firstregion and above the first associated complementary line conductor inthe second region and the second true line conductor is disposed belowthe second associated complementary line conductor in the first andsecond regions.
 13. The method of claim 12, wherein the firstinterconnection layer is disposed below first portions of the first pairof line conductors in the vertical twisting region, the secondinterconnection layer is disposed below second portions of the firstpaired line conductors in the vertical twisting region.
 14. The methodof claim 13, wherein the first interconnection layer is non-overlappingwith the second interconnection layer.
 15. The method of claim 14,wherein the first and second true line conductors include polycide. 16.The method of claim 14, wherein the first and second associatedcomplementary line conductors include metal.
 17. The method of claim 14,wherein the first interconnection layer includes polysilicon.
 18. Themethod of claim 14, wherein the second interconnection layer includesactive areas.
 19. The method of claim 14, wherein a first pitch betweenthe first pair of line conductors and the second pair of line conductorsin the first region is substantially similar to a second pitch betweenthe first pair of line conductors and the second pair of line conductorsin the second region.
 20. The method of claim 14, wherein: the firstinterconnection layer connects to the second associated complementaryline conductor through first and second contact holes disposedsubstantially at respective first and second peripheral portions of thefirst interconnection layer in the vertical twisting region; the firsttrue line conductor in the first region connects to the first true lineconductor in the second region through a third contact hole in thevertical twisting region; and the first associated complementary lineconductor in the first region connects to the first associatedcomplementary line conductor in the second region through a fourthcontact hole in the vertical twisting region.
 21. The method of claim14, wherein the second interconnection layer connects to the second trueline conductor through first and second overlapping interconnectsdisposed substantially at respective first and second peripheralportions of the second interconnection layer in the vertical twistingregion.
 22. The method of claim 12, wherein: the first and secondassociated complementary line conductors include metal; the firstinterconnection layer includes polysilicon and the secondinterconnection layer includes active areas; a first pitch between thefirst pair of line conductors and the second pair of line conductors inthe first region is substantially similar to a second pitch between thefirst pair of line conductors and the second pair of line conductors inthe second region; the first interconnection layer connects to thesecond associated complementary line conductor through first and secondcontact holes disposed substantially at respective first and secondperipheral portions of the first interconnection layer in the verticaltwisting region; the first true line conductor in the first regionconnects to the first true line conductor in the second region through athird contact hole in the vertical twisting region; the first associatedcomplementary line conductor in the first region connects to the firstassociated complementary line conductor in the second region through afourth contact hole in the vertical twisting region; and the secondinterconnection layer connects to the second true line conductor throughfirst and second overlapping interconnects disposed substantially atrespective first and second peripheral portions of the secondinterconnection layer in the vertical twisting region.
 23. A method forforming an interconnection array in an integrated circuit, comprising:forming a first twisting region; forming a first pair of true andcomplementary conductive paths spanning from a left side of the firsttwisting region to a right side of the first twisting region; andforming a second pair of true and complementary conductive pathsspanning from a left side of the first twisting region to a right sideof the first twisting region; wherein the first twisting region affectsa vertical twist in the first pair of conductive paths between the leftside to the right side, wherein the first twisting region does notaffect a horizontal twist of the second pair of conductive paths betweenthe left side to the right side, and wherein the first twisting regiondoes not affect a vertical twist in the second pair of conductive pathsbetween the left side to the right side, although the first twistingregion routes both of the conductive paths of the second pair todifferent layers in the integrated circuit using contacts or vias. 24.The method of claim 23, wherein the first twisting region affects avertical twist in the first pair of conductive paths by routing theconductive paths to different layers in the integrated circuit usingcontacts or vias.
 25. The method of claim 23, wherein the true andcomplementary conductive paths of the first pair are vertically spacedfrom each other on the right and left sides, and wherein the true andcomplementary conductive paths of the second pair are vertically spacedfrom each other on the right and left sides.
 26. The method of claim 23,wherein the first pair of conductive paths is horizontally adjacent thesecond pair of conductive paths.
 27. The method of claim 23, furthercomprising: forming a second twisting region, wherein the secondtwisting region is horizontally displaced from the first twisting regionalong an axis generally parallel to an axis of the conductive pathpairs; wherein the second twisting region affects a vertical twist inthe second pair of conductive paths between the left side to the rightside, wherein the second twisting region does not affect a horizontaltwist of the first pair of conductive paths between the left side to theright side, and wherein the second twisting region does not affect avertical twist in the first pair of conductive paths between the leftside to the right side, although the second twisting region routes bothof the conductive paths of the first pair to different layers in theintegrated circuit using contacts or vias.
 28. The method of claim 23,wherein the true conductive paths comprise a first conductive layer inthe left and right sides.
 29. The method of claim 28, wherein the firstconductive layer comprises polycide.
 30. The method of claim 28, whereinthe complementary conductive paths comprise a second conductive layer inthe left and right sides, wherein the second conductive layer is abovethe first conductive layer.
 31. The method of claim 30, wherein thecomplementary conductive paths comprise a metal.
 32. The method of claim30, wherein second complementary conductive path comprises polysiliconin the twisting region.
 33. The method of claim 32, wherein the secondtrue conductive path comprises an active area layer formed in asemiconductive substrate in the twisting region.
 34. A method forforming an interconnection array in an integrated circuit, comprising: afirst twisting region having left and right sides adjacent thereto; afirst pair of true and complementary conductive paths present in thefirst twisting region, in the left side, and in the right side; and asecond pair of true and complementary conductive paths present in thefirst twisting region, in the left side, and in the right side; whereinthe first twisting region affects a vertical twist in the first pair ofconductive paths between the left side to the right side, wherein thefirst twisting region does not affect a horizontal twist of the secondpair of conductive paths between the left side to the right side, andwherein the first twisting region does not affect a vertical twist inthe second pair of conductive paths between the left side to the rightside, although the first twisting region routes both of the conductivepaths of the second pair to different layers in the integrated circuitusing contacts or vias.
 35. The method of claim 34, wherein the firstpair of conductive paths are formed along an first axis in the left sideand in the right side, and wherein the second pair of conductive pathsare formed along a second axis in the left side and in the right side.36. The method of claim 35, wherein the first twisting region affects avertical twist in the first pair of conductive paths by routing theconductive paths to different layers in the integrated circuit usingcontacts or vias.
 37. The method of claim 35, wherein the true andcomplementary conductive paths of the first pair are vertically spacedfrom each other on the right and left sides, and wherein the true andcomplementary conductive paths of the second pair are vertically spacedfrom each other on the right and left sides.
 38. The method of claim 35,wherein the first pair of conductive paths is horizontally adjacent thesecond pair of conductive paths.
 39. The method of claim 35, furthercomprising: forming a second twisting region having left and right sidesadjacent thereto, wherein the second twisting region is horizontallydisplaced along an axis generally parallel to the first or second axes;wherein the second twisting region affects a vertical twist in thesecond pair of conductive paths between the left side to the right side,and wherein the second twisting region does not affect a horizontaltwist of the first pair of conductive paths between the left side to theright side, and wherein the second twisting region does not affect avertical twist in the first pair of conductive paths between the leftside to the right side, although the second twisting region routes bothof the conductive paths of the first pair to different layers in theintegrated circuit using contacts or vias.
 40. The method of claim 34,wherein the true conductive paths comprise a first conductive layer inthe left and right sides.
 41. The method of claim 40, wherein the firstconductive layer comprises polycide.
 42. The method of claim 40, whereinthe complementary conductive paths comprise a second conductive layer inthe left and right sides, wherein the second conductive layer is abovethe first conductive layer.
 43. The method of claim 42, wherein thecomplementary conductive paths comprise a metal.
 44. The method of claim42, wherein second complementary conductive path comprises polysiliconin the twisting region.
 45. The method of claim 44, wherein the secondtrue conductive path comprises an active area layer formed in asemiconductive substrate in the twisting region.